Cycas arnhemica is a species of cycad in the genus Cycas, native to Australia, in the northwest of Northern Territory in Arnhem Land, after which it is named.

The stems are erect, growing to 1.5-2.5 m tall. The leaves are numerous, flat, 70–160 cm long, pinnate, with 160-260 leaflets; the new young leaves are deep white tomentose at first, becoming bright to dark green, moderately glossy above, the down often persisting on the underside.

There are three subspecies:

• Cycas arnhemica subsp. arnhemica. Leaflets broad, 5-6.5 mm wide.
• Cycas arnhemica subsp. muninga. Leaflets slender, 3.5-5.5 mm wide; seeds over 32 mm wide.
• Cycas arnhemica subsp. natja. Leaflets slender, 3.5-5.5 mm wide; seeds under 32 mm wide.

The female cones are open, 15–24 cm long, with grey sporophylls and orange hairs, with two to six ovules per sporophyll. Triangular lamina, toothed, with an apical spine. The seeds are 28–32 mm long and 25–29 mm broad, with an orange sarcotesta when ripe. The male cones solitary, ovoid, 18–36 cm long and 6.5–12 cm diameter, also covered in orange hairs.

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